The present invention relates to a controller for an automatic transmission used in an automobile or the like.
Automatic transmissions have been widely used as transmissions for automobiles etc. With a conventional automatic transmission, taking a drive shaft of a driving motor, such as an engine, as input, a turbine of an input shaft of a torque converter is caused to rotate, and the input is converted at a specified gear ratio by a planetary gear connected to the input shaft and conveyed to an output shaft. A plurality of frictional engagement devices for clutches or brakes are provided between the input shaft and the output shaft in order to regulate movement of this planetary gear, and gear ratio is switched depending on which of these frictional engagement devices are engaged. Normally, frictional engagement devices that are caused to engage are switched according to input shaft rotation speed and throttle opening amount to switch gear ratios.
As a general rule, a gear shift controller for an automatic transmission sequentially progresses through gear shift start time control, torque phase control, inertia phase control, and gear shift completion time control. Here, the torque phase is a zone where engagement side clutches are engaged and respective conveyed torque is being converted while disengaging disengagement side clutches, and the inertia phase is a zone where input shaft rotation speed is drawn towards a rotation speed determined by output shaft rotation speed and target gear ratio.
In the torque phase, if engagement side clutch engagement is slow compared to the timing of disengaging the disengagement side clutch, at the time of disengaging the disengagement side clutch, torque conveyed to the engagement side clutch is sufficiently small compared to input torque for turbine speed to suddenly increase. On the other hand, the engagement side clutch engagement timing is early, conveyed torque through the engagement side clutch at the time of disengaging the disengagement side clutch becomes large and turbine speed drops rapidly.
In the inertia phase, regulation of the input shaft rotation speed is carried out by causing frictional engagement devices to engage, but at this time if the frictional engagement devices are suddenly engaged, output torque changes suddenly generating gear shift shock. Also, since the time required to change gear is prolonged if the frictional engagement devices are engaged slowly, this is undesirable from the driver""s point of view and also lowers the durability of the frictional engagement devices.
An advantage of the present invention is that it provides an automatic transmission controller that can appropriately perform an appropriate gear shift operation.
With the present invention, in the torque phase engagement side clutch coupling force is set by a setting device. A coupling force controller then determines disengagement side clutch coupling force control amount according to the engagement side clutch control state using a physical model of the automatic transmission.
It is therefore possible to carry out adjustment of coupling force for the engagement side clutches and the disengagement side clutches by changing engagement side clutch coupling force setting without changing both the engagement side clutch coupling force and the disengagement side clutch coupling force by trial and error. Also, in the physical model, timing adjustments can be carried out easily by adjusting a specified offset.
In the inertia phase it is appropriate to perform engine torque control. At this time, it is preferable to compute a drive torque target value using a physical equation that uses an inertia phase time target value and a conveyed torque estimation means estimation value. In this way it becomes necessary to use a control map in order to obtain a drive torque command value, and it is possible to omit a task of experimentally ascertaining a suitable value for the drive torque command value. Accordingly, it is possible to significantly reduce control map creation time while at the same time reconcile the mutual incompatibility between gear shift shock and gear shift time in the inertia phase.